A signal processing technique for electrically processing a sine-wave signal and a cosine-wave signal supplied from a signal generating source for a pulse encoder, and improving the resolution of the encoder is conventionally known.
A conventional signal processing apparatus for a pulse encoder comprises, for example, a rotary code plate mounted on a shaft of a motor or the like, in which a plurality of slits are formed, a fixed code plate in which a plurality of slits are formed, a signal generating source having a light-emitting diode and a photodiode, and a signal processing apparatus. The signal processing apparatus comprises a plurality of resistor and comparator array, and the resolution of the encoder is increased by the resistors and the comparator array. For example, when the resolution of the encoder is increased 10 times, 20 circuits each comprising resistors and a comparator are required, and 20 types of signals each having different phases are generated.
When the resolution of the encoder is increased 10 times, for example, 60 resistors and 20 comparator are required in order to improve the resolution of the encoder. Therefore, the cost required for the resistors and the comparator array is increased and the signal processing apparatus becomes bulky. In addition, the conventional signal processing apparatus for the pulse encoder cannot confirm the intensity of a signal supplied from the signal generating source. Therefore, when a signal having an insufficient intensity is processed, an erroneous pulse signal is often output.